Method for making electric discharge lamps



Jan. E7 150 R. L. BREADNER ET AL 2,494,857

mz'mon FOR MAKING ELECTRIC DISCHARGE LAMPS Filed Feb. 25, 1946 lnven tovs Robert Leonard Breadner Henry Gr ainger Jenkins, C amtas Henry Simms', b5 EMMJ M Them Ai kovneg.

Patented Jan. 17, 1950 UNITED STATE 4 Claims.

The present invention relates to the method of making electric discharge lamps having long positive-column discharge paths. The invention is applicable both to cold cathode lamps of the kind usually operated from high voltage and also to hot cathode lamps of the kind frequently operated from ordinary supply voltages. The invention is therefore applicable to hot cathode lamps having their envelopes coated internally with fluorescent powder, in which the discharge passes through mercury vapour usually admixed with a few millimetres pressure of a rare gas such as argon. Such lamps are now of great importance as light sources.

I The. dimensions of these fluorescent lamps, which are usually but not necessarily of circular cross-section,-may vary, for example, from a few inches to several feet in length and from to 2" in mean diameter. They are usually made by mass production methods and are, therefore, gen- S PATENT OFFICE METHOD FOR MAKING ELECTRIC DISCHARGE LAMPS Robert Leonard Breadner, Kenton, Henry Grainger Jenkins, Pinner, and Charles Henry Simms, Twickenham, England, assignors to General Electric Company, a corporation of New York Application February 25, 1946, Serial No. 650,068

In Great Britain December 21, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires December 21, 1964 erally straight lengths of tubing. Other shapes,

such as grids, spirals, etc., have often been proposed but such shapes do not lend themselves readily to mass production methods and can be obtained, in general, only by manipulation by skilled craftsmen. The operation becomes progressively more difficult to perform as the diameter of the tubing is increased, and as the radius of curvature is decreased.

The simple straight tube has several practical disadvantages. length, it obviously requires considerable care in handling to avoid mechanical breakage.

Furthermore, since the electrodes are situated at opposite ends of the tube, a straight tube will require two widely separated external contacts or caps which may need to be very accurately spaced apart to fit into a housing with pre-set sockets for the supply of electric power. Also large linear sources are difiicult to deal with optically and where a fitting is used this is large and costly in relation to the wattage of the lamp. For these reasons fluorescent lamps have been virtually ruled out forst'r'eet lighting where the excellent spectral characteristics of their light might be used to great advantage.

The invention is concerned with the method of making discharge lamps of the type in which compactness is secured by giving the discharge path between two electrodes a spiral, zig-zag or 50 face of this disc is laid a spiral strip or the 11k As it may be several feet in drawing in which other sinuous shape and in which the discharge path is a channel formed between two vitreous components sealed together, one or both of the components having one or more upstanding ridges which separate adjacent parts of the discharge path from one another.

It is the object of the present invention to provide an improved method of constructing lamps of this kind.

According to the present invention, a method of constructing a lamp of the type specified comprises the steps of applying heat to fuse said two components together along said ridges and applying gas pressure to the spaces between said ridges whilst one or both said components are rendered plastic by heating in order to enlarge said spaces.

The gas pressure is conveniently air pressure and may be applied whilst the said components are within a mould which determines the contour of a part of the wall bounding the said spaces.

The present invention further provides a method of constructing a lamp of the type specified which comprises the steps of applying one or more strips or the like (for instance rods, small bore tubes) of vitreous material to a surface of one of the said components along the line or lines where the said ridges are to be formed, placing the two components together in such a manner that they are spaced apart by the applied vitreous material, heating the components to cause them to weld to the applied vitreous material and expanding the passage or passages between the applied vitreous material by blowing.

The invention will be described by way of example with reference to the accompanying Fig.;1 is a plan view of one component of a lamp according to the invention,

. Fig. 2 is a view in sectional elevation of the two components of the embodiment of Fig. 1 at one stage in the manufacture,

Fig. 3 is a view in sectional elevation of th lamp of Fig. 2 after expanding the discharge pas sages by blowing, and I Figs. 4 and 5 show in sectional elevation two stages in the manufacture of a different form of lamp according to the invention.

Referring to Fig. 1, one component shown is i the form of a flat disc H) of glass. on one sur ll of glass with its outer end turned inward and joined to the second turn of the spiral at [2 in order that the channel formed between the turns of the spiral shall be closed at its outer end. The strip II is then fused to the disc ID by heating. Tubulations l3 and it are sealed to the disc to provide connections with the outer and inner ends respectively of the, channel. The component I0 is then covered by a second component l5 also in the form of a disc of glass as shown in Fig. 2. The upstanding ridges constituted by the spiral strip ll then abut or substantially abut against the disc I5. The discs and [5 are thenheated, as a whole or selectively along the. ridges II, in order to fuse the two components together along the crests of the ridges H. Qne of. the tubulations is then closed and air is blown into the other to exert pressure within the spaces beis rendered plastic by heating. The spaces are thus expanded and assume a shape somewhat as shown in Fig. 3.

Preferably the expanding of the passages is carried out whilst the components It) and I5 are within a suitably shaped mould 2| which then definesthe outer contour of the exposed parts of the walls.

Electrodes are preferably mounted. in known manner on pinches formed in the tubulations l3 and I4. There is then provided a spiral-shaped discharge passage extending between the two electrodes. This passage is evacuated and filled with a suitable gas or vapour or a mixture of gas or vapour and sealed off. If desired the inner with luminescent powder, for example by. dusting using the method described in British patent specification No. 460,756.

Referring to Fig. 4, both components l6 and I! are in this case in the form of cylinders with domed ends. They are conveniently blown to the shape shown and before they are assembled a strip or the like l8 of glass is laid in helical form around the inner component I! and is fused thereto by heating. The lower end of the strip 18 is turned upwards and joined to the second turn of the helix in order to close the lower end of the helical passage. This is not shown in the drawing however. Tubulations l9 and 20 are sealedthrough the inner component I! toprovide connections with the two ends of the helical passage formed between the upstanding ridges constituted by the strip I 8.

The inner component I! is then placed within the outer component It, as shown in: Fig. 4, and heat is applied to fuse the two components together along the crests-of the ridges. One of the tubes H5 or I! is then closed and air is blown into. the other whilst the components [6 and H are heated. The envelope then assumes a form somewhatas shown in Fig. 5. The envelope of Figs. 4 and 5 may be provided with a fluorescent coating, if desired, fitted with electrodes, evacuated and gas filled as described with reference to Figs. 1 to 3.

5, the expansion of the discharge passage may be effected by blowing into a mould which defines surface of the discharge passage may be coated u With the form of envelope shown in Figs. 4' and tween the ridges l l and at the sametimethe glass 4 the outer contour. In-this case, however, the use of an inner mould is usually not convenient.

In both embodiments the sealing together of the two components along the crests of the ridges l l and I8 may be carried out in a number of different ways, for example by collapsing the component 15 or [B on to the ridges II or I8 of the other component'by general heating or by local and progressive melting with a small flame alon the ridges. In the latter method, the continuous travel of the flame along the ridges can be controlled by well-known mechanical means. Other methods of performing the sealing of the two components together will be obvious to those skilled in the art, for example the components may be suitably heated and rolled or tooled into contact.

The passage or passages defined by the added glass'may be of any other suitable, sinuous shape, for example a two-start spiral or helix or a single or two-start zig-zag.

If desired ridges may be provided on both components, these ridges being fused together in any suitable way along their crests. It is not essential that the ridges should be constituted by added glass. One or both components may be formed with suitable ridges by moulding. After fusing the components together the discharge passage. is expanded by blowing as already described.

We claim:

1. A method of constructing an electric discharge lamp in which the discharge path between two electrodes has a sinuous sha-pe'wwith juxtaposed portions substantially circular in cross-'- section, and in which said discharge path is a channel'formed between two vitreous components sealed together, which method comprises the'steps of applying to a surface of at least one of said components strip-like vitreous material, fusing said material to said component by heating, placing said two' components in juxtaposition in such a manner that said vitreous material constitutes part of "the wall of a sinuous passage between said components, heating said components to fuse them together along said vitreous material,.and applying gas pressure to the said passage whilst at least one Of said componentsis rendered plastic by heating in order to enlarge said passage to a substantially circular "cross-section.

21 A method according to claim 1, wherein said components are in the form of flat sheets.

3. A method according to claim 1, wherein said components are of hollow shape, one being arranged within the other.

4. A method according to claim 1, wherein said components are of substantially cylindrical shape one being arranged within the other.

ROBERT LEONARD BREADNER; HENRY GRAINGER'JENH'NS. CHARLES HENRY SIIMMS.

REFERENCES CITED The following references are of record. in the file of this patent:

UNITED STATES PATENTS Number 

